Dear Wolfgang Denk,
Dear Reinhard Meyer,
In message4CC66A67.4000608@emk-elektronik.de you wrote:
It fails in case the timer wraps around.
Assume 32 bit counters, start time = 0xFFFFFFF0, delay = 0x20. It will compute end = 0x10, the while codition is immediately false, and you don't have any delay at all, which most probably generates a false error condition.
I used and assumed a 64 bit counter, that will not wrap around while our civilization still exists...
The code is still wrong, and as a simple correct implementation exists there is no excuse for using such incorrect code.
Please fix that!
Agreed here. People are invited to dig through u-boot and find all those places.
If get_ticks() is only 32 bits worth, both methods will misbehave at a 32 bit wrap over.
No.
start = time(); while ((time() - start)< delay) ...
This works much better (assuming unsigned arithmetics).
True, provided the underlying timer is really 64 bits, otherwise this fails, too...
You are wrong. Try for example this:
--------------------- snip ------------------- #include <stdio.h>
int main(void) { unsigned int time = 0xFFFFFFF0; unsigned int delay = 0x20; unsigned int start;
You are wrong here, because you take it out of context. My "demo" is using the (declared as) 64 bit function get_ticks(). I mentioned above that this function MUST be truly returning 64 bits worth of (incrementing) value to make any version work. If get_ticks() just returns a 32 bit counter value neither method will work reliably. Just check all implementations that this function is implemented correctly.